When giving animals injections, syringes containing medication are often mounted on poles. The purpose of mounting the syringe onto a pole is to provide a greater reach to a farmer or rancher endeavouring to administer an injection to an animal. Without the use of a pole or some form of projectile it is extremely difficult to get close enough to an animal to administer an injection.
Once a needle from a pole mounted syringe is inserted into an animal's hide, the animal has a tendency to bolt. If the farmer or rancher continues to hold onto the pole when the animal bolts, the needle is withdrawn prematurely leaving unadministered medication in the syringe. If the farmer or rancher lets go of the pole, the pole will be dragged along the ground, which will also withdrawn the needle prematurely from the animal's hide.
Attempts have been made to develop impact releasable pole mounted syringes. An example of such an impact releasable pole mounted syringe is U.S. Pat. No. 4,684,366 which issued to Denny et al in 1987. The Denny reference discloses a pole with a retractable collar at one end having a plurality of integral spring triggers. A syringe is inserted part way into a remote end of the retractable collar. The other end of the retractable collar has a spring biased plunger which is maintained in a compressed condition by the triggers. The interior surfaces of each of the triggers are bevelled and act like cam surfaces. Upon impact with an animal, the syringe to forced all the way into the retractable collar. As the syringe moves into the retractable collar, it engages the bevelled cam surfaces on the interior of the triggers forcing the triggers outwardly. With the triggers forced outwardly, the plunger is no longer constrained and is urged by the biasing force of the spring forward to jettison the retractable collar. The problem with the release mechanism as taught by Denny et al is it's complexity.